The present invention relates to biomedical electrodes, particularly an electrolyte formulation for use with a single use, disposable biomedical electrode, which provides improved skin penetration and conductivity, and will be described with particular reference thereto. It should be appreciated, however, that the invention is also applicable to a wide variety of biomedical electrodes.
Biomedical electrodes of various types are available for transferring current signals between the skin of a person and an external circuit. Electrodes used in electrocardiography (ECG) are classed as xe2x80x9cmonitoringxe2x80x9d or xe2x80x9cdiagnostic.xe2x80x9d Monitoring electrodes are those which are used in demanding or lengthy applications, such as stress testing, critical care, heart monitoring, and the like. Diagnostic electrodes are generally used for less demanding applications and short term diagnoses.
In order to provide good electrode contact between an electrical terminal and the person""s skin, it is customary to apply an electrolyte between the electrical terminal and the skin. The electrolyte may be absorbed in a support medium, such as a sponge, or located in a chamber which can be closed off by a porous membrane.
ECG electrodes fall into two general types, namely electrodes in the form of a flat patch unit, or electrodes comprising a pre-gelled electrolyte in a domed housing. Both types of electrode are generally passive, in that they lie passively on the skin surface waiting to pick up signals from within the body.
U.S. Pat. Nos. 4,216,969 and 4,693,711, to Bremer, et al. disclose examples of domed disposable biomedical electrodes for pressurized skin contact. The electrodes include a vaulted dome-like electrolyte-containing chamber or cavity which is closed at its open end by a highly flexible, conformable and hydrophobic microporous membrane. For storage, the membrane is covered with an adhesively secured protective film which is adapted to be stripped prior to adhesively securing the electrode to the skin of a patient. When downward pressure is applied to the vaulted housing, the housing is physically compressed and electrolyte within the chamber is pumped through the membrane into positive and low-electrical resistance contact with the skin surface of the patient. The housing is configured to maintain a positive, sustained pressure of the electrolyte against the skin surface, providing a low-impedance connection between the skin of the patient and the electrode terminal.
The signals which cardiologists and other diagnosticians seek to detect are sometimes very low. For example, signals generated by the heart are of the order of 0.005 volts. The outer layers of the epidermis, particularly the dead skin layer or stratum corneum, are poorly conducting. Typically, the skin surface impedance is around 54 kilo ohms, which provides a barrier to the reception of such minute signals by present types of electrolytes. The signal must traverse both the skin surface and the electrode before it is detected by the electrocardiographic instrument.
There remains a need for an electrolyte capable of penetrating the outer epidermal layers for improved signal conduction.
The present invention provides for a new and improved electrode system and electrolyte composition which overcome the above-referenced problems and others.
In accordance with one aspect of the present invention, an electrolyte composition for use in a biomedical electrode assembly is provided. The electrolyte composition includes an electrically conducting salt system and a salt of pyrrolidone carboxylic acid.
In accordance with another aspect of the present invention, an electrolyte composition for use in a biomedical electrode assembly is provided. The electrolyte comprises, by weight:
a) 1-14% of an electrically conducting salt system;
b) 10-25% of a skin penetration agent;
c) 0-10% of a thickener;
d) 0.001-5% of a surfactant;
e) 0-10% of a pH modifier; and,
f) water.
In accordance with yet another aspect of the present invention, a single-use biomedical electrode assembly for receiving body-generated electrical signals at a skin surface of a subject is provided. The electrode assembly includes an inverted, deflectable, generally dish-shaped housing having a vaulted dome-like roof, a base, and an integrally formed, laterally extending annular flange at the base. The housing presents a downwardly directed opening bounded by an inward edge of the flange. A porous, fluid-permeable membrane covers the housing opening. The housing and the membrane define a chamber for an electrolyte. An electrolyte fills the chamber. The electrolyte includes an electrically conducting salt system and a skin penetration agent for increasing a penetration of the electrolyte through an outer layer of the subject""s skin. The membrane is permeable to the electrolyte when a pressure is applied to the electrolyte. An electrically-conductive terminal is sealed to and extends through the roof of the housing and provides electrically-conductive communication between the exterior of the housing and the electrolyte within the chamber.
In accordance with yet another aspect of the present invention, a single-use biomedical electrode assembly for receiving body-generated electrical signals at a skin surface of a subject is provided. The electrode assembly includes a base layer of a first non-porous material and an intermediate layer of a second non-porous material. The intermediate layer defines an aperture and is sealed at a first surface to an inner surface of the base layer around the aperture to define a chamber. An electrolyte fills the chamber. The electrolyte includes an electrically conducting salt system and a skin penetration agent for increasing a penetration of the electrolyte through an outer layer of the subject""s skin. An electrode material provides electrically-conductive communication between the exterior of the electrode assembly and the electrolyte within the chamber.
One advantage of the present invention resides in improved skin penetration and enhanced electrical conductivity of current signals while maintaining a desirable ionic and pH balance.
Another advantage of the present invention is that the electrolyte is suited for use in a low cost, disposable electrode, with extended shelf life.
Yet another advantage of the present invention is its applicability to a variety of measurements, including monitoring and stress testing, diagnostic electrocardiograms (ECG), and other applications.
A further advantage of the present invention is that the electrolyte functions effectively over a period of several days, and is suited to long term studies.
A yet further advantage of the present invention is that the skin preparation is reduced or eliminated.
A yet still further advantage of the present invention is the provision of an electrolyte with emollients for improved skin comfort.
Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiment.